Starter for free piston motor compressors



July 3, 1947. P. MOLLEJANS ETAL [2,423,720

' swzm: FonvFRma rrsron MOTOR, courmassons Filed Nov. 12. 1941 2sheets-sheet 1 J2 g 4/0 I ,Ivenzs PazzZ MZZeJzns and) Ii'anz Jl/ugebauerJy MJ Am'ney l Jilly 3, l947- n P. MULLEJANs ETAL `2,423,720

STARTER FOR FREE PISTON MOTOR COIIPRESSORS Filed Nov. l2, 1941 2Sheets-Sheet 2 l J5 J 4/0 I Y T" ,Ill llllllllll l 33 Hull' Z'nvenbrsfana Maag/12ms and, l ZW/'nmz Nealgeauz' the motorpart by a PatentedJuly 8, 1947 STARTER. Fon FREE ris'roN Moron coMPm-:ssons l PaulMllejans, Lindau,

Munich-Allach, Germany;

and Franz Neugebauer,

vested in the .littor-l ney General of the United States ApplicationNovember 12, 1941, Serial No. 418,666 In Germany November 29, 1940 10Claims. (Cl. 2210-56) This invention relates to a device for startlapiston forming part of the flying mass operates, is filled with thestarting fluid under pressure. Then the locking device is released. Nowthe fluid under pressure is capable of displacing the ilying mass,whereby it expands, doing Work, thus eiecting the compression of thecylinder charge immediately or after reversal ,ofV

:the'direction of motion.

Furthermore, it is well -known in free piston motor compressors withmultistage compression to l.utilize all or one of the working spaces ofthe .stages of compression as starting spaces.

The upper and lower limits of the pressure of the starting iluid,existing in the starting space immediately before setting the flyingmass going are positively controlled.

The lower limit is determined by the fact that the motor cylinder chargeis to be subjected to the compression required for regular ignition, i.e. for initiating the first motor-working stroke (which is especiallyimportant when the motor part as in the usual case 'works according tothe Diesel process). The lower` limit of pressure is further determinedby the fact that the spaces used for starting must be able to interceptthe energy" produced in the first Working stroke of suiliciently strongcushion of compressed fluid. tant when separate spaces are used forstarting, asin .th case oi multistage compressors, because then theoutlet pressure corresponding to other hand this upper limit is alsodetermined bythe fact that the compression of the motor cylinder chargemust not exceed a certain value, as otherwise the pressures ofcombustion would become so high that the motor part could be damaged.

The importance to be imputed to the right adjustment of the pressure ofthe starting fluid in the starting spaces, as regards safe starting asWell as avoiding detrimental disturbances, makes it desirable to provideeillcient safety guards for maintaining'the right pressure in thestarting spaces.

Therefore an object of this invention is to provide means forautomatically maintaining the right starting pressure so that thepressure of the fluid existing in thestarting spaces im-y mediatelybefore setting in motion the flying mass does not surpass apredetern'iinedv upper or lower limit. These limits are generally re-`mote from each other, but may also coincide.

i AsA means to prevent exceeding the upper limit of pressure there areconsidered: j

(l) A `pressure controlling device (pressure reducing valve) insertedinto the line for admitting fluid under pressure from a container .tothe starting space which device throttles an KK optional pressure ofcompressed fluid automati- This is especially impornormal operation inthese compression spaces is only gradually established in the course ofa. p1u rality of strokes.

The upper limit of pressure is of course determined. on the one hand. bythe strength of the walls confining these spaces (for instance, in casethat a compressor space Working with low outlet pressure in the normaloperation is used, this pressure cannot be chosen higher or essentiallyhigher than this outlet pressure). On the cally down to a pressurecorresponding to the upper limit of pressure in the starting space;

(2) An overflow valve inserted into the line connecting the startingspace with a space of lower pressure and opening as soon as apredetermined pressure in the starting space is attained therebyallowing fluid under pressure to enter the space of lower pressure:

(3) A safety valve inserted into an outlet of y the starting space orbehind the overow valve and opening a passage to the open air as soon asa predetermined pressure in the starting space, or in the spme behindthe overow valve respectively, is attained.

Means to prevent exceeding the lower limit of pressure are:

(fa) A releasing member charged 'with the pressure of the fluid underpressure coming from the starting space and releasing a locking `memberretaining the flying mass only after this the pressure required forreleasing the locking member.

(b) An overilow valve in the line between the' starting space and aspace of lower pressure, for instance, the working space of a releasingmember, the effective pressure of which is lower than theopening-pressure of the overilow valve. This valve prevents the iluidunder pressure from flowing oi to a space of lower pressure or to thereleasing member, before the starting space is lled with the fluid underpressure up to the lower limit of pressure.

By the indicated means even a double safety guard may be obtainedagalnstan excessively high or low starting pressure.' safety guard adisturbance can only occur when both safety members fail to operate atthe same time. The probability of such a disturbance is very remote incase of a simple safety guard. This is especially true when both safetymembers are of diierent kind, as safety members f the same kind may incertain cases be liable to the same defect and therefore may failsimultaneously more easily than' two members of diierent kind.

As a double safety guard against excessive pressure, a pressure-reducingvalve in the supply pipe and an overow valve in an outlet of thestarting space, may be provided iny combination with a safety valve. 4

A double safety guard against too low pressure is formed by a releasingmember connected over an overflow valve with the starting space, theeffective pressure of said member approximating the opening pressurey ofthe overilow valve.

'Ihe invention proves very valuable also in case that a plurality ofstarting spaces is provided in an engine, which spaces are to be lledwith starting iluids of different pressure. In this case, the startingspaces are connected with one an# other, that is, the last startingspace which con# tains the gas of the lowest pressure is connected withthe releasing member by pipes having over? cally ll with uid underpressure up to the lower .limit of pressure adjoined to each of thestarting spaces and determined by its overow valve.

Also in this case a double safety guard against excessive pressure ispossible for each starting space by inserting, into the pipe between theoverflow valve ofv the one starting space to the next one, a pressurecontrolling deviceadjusted' to the highest starting pressure admissiblefor the subsequent starting space.

The invention is illustrated in the annexed drawings, of which With suchdouble v Fig. 1 is a vertical, axial cross-section of a starterconstructed in accordance with the invention comprising two workingspaces, a pressure reducing valve, an overilow valve, a safety* valveand a locking and releasing device;

Fig. 2 is a similar cross-section of a starter in which the engine isformed as a multistage com- Fig. 4 illustrates a simplification in casethe lower limit of pressure in the starting` space having the lowestpressure is equal towzero.Y

The drawings show diagrammatically several modifications oftheinvention, in each. case the left half of a free piston motor compressorprovided with oppositely moving flying masses. Corresponding parts ofthe figures are denoted by the same reference letters.

In the arrangement shown in Fig. 1 a compression cylinder 2 isconnected-on the one hand with a motor cylinder I and on the `other handwith a cylinder 3. 'I'he flying mass is composed of the motor piston 3the compression piston I and a. piston 6 operating in the cylinder 3.The compression cylinder 2 comprises two working spaces: the compressionspace proper 3 and the working space 3 turned toward the motor cylinderand working as a scavenging pump. The

scavenging air iiows from the space 9 to a, con-y instance,` as acushion or as a higher stage of compression. The compressed iluid forstarting is stored under high pressure in a container 2l which may berefilled through a pipe 2I coming from a source of compressed fluid, forinstance. a compressor and including a shut-off member 22. Asecond'shut-oif member 23 connects the container 20 with a.withdrawalline 24 leading to a reducing valve 25 which throttles the pressureofthe container down to the maximum pressure admissible in the startingspace I2. `From the reducing valve 25 a pipe 26 including a handoperatedstarting valve 21 leads to the starting space I2. A pipe 28 branchingoil? behind the hand-operated starting valve 21 leads to a similarstarting space of the other half of the engine.

A rod 30 is rmly secured to the compression piston and conductedoutwards, which rod may simultaneously form part of the connecting gearcompelling the oppositely moving ilying masses to synchronous motion. Atooth or catch 3| is lixed on the rod 30 which may engage a pawl 33swingable abut a stationary fulcrum 32. This pawl is connected with apiston 4I sliding in a stationary cylinder 40. Fluid under pressure maybe supplied through the pipe 36 to the space 42 above the piston 4I. Apressure spring 43 acts upon the back side of the piston. An auxiliarypawl 38 is further connected with the paw1,33 arranged to engage a.stationary abutment 3l when pawl 33 is released from the tooth 3lagainst the action of the spring 43. whereby pawl 33 isprevented fromcatching again after being released. By means of a handle ll provided onthe auxiliary pawl 38 the latter may be released from the abutment 33 toinitiate a new starting operation. From the starting space I2 a duct 3|leads to an overiiow valve 45 connected with the pipe 36 from which aduct 31 is branched oif which leads tothe open air over a safety valve48. l

In order to make the operation of the contrivance as clear as possible,the following nupressures:

merical values may be assumed for the single Superatmospheric pressure,

atmospheres Highest admissible pressure in starting space 25 I dmissiblepressure instarting space The safety valve 46 may be adjusted to 5 Thereleasing member 4I may be adjusted The resulting operation is asfollows:

The flying mass e, 5, Is is at first shifted to the stage compressor, sothat the cylinder 2 and the piston 5 with'the working space 8 form theiirst stage oi' compression, and the cy1inder'3 and the piston -Ii withthe working space I2 form the a /second stage of compression. In thiscase` the working spaces 8 and I2 areto be used as start-` ing spaces atthe inner dead center position of the compressorv pistons, the pressureof starting uid' to be admitted to these spaces correspondl ing to theoutlet pressures of the stages of compression obtained in the normaloperation. Therefore the space -8 is to be charged with compressedstarting gas of an essentially lower pressure than the space I2. The.pressure valves I and 52 are so -arranged that the ducts leading fromthe compression working spaceto the ducts in which these valves arelocated kare closed by the pistons 50116, respectively, in the startingposition,of said'pistons, as shown in Fig. 2. In

left by means of rod 30 until the pawl 33 under zo order to preventthebompressed starting as from the action of the spring 43 can engagethe catch 3l.. The shut-off member I4 controlling the starting space I2is closed and the shut-off valve on the container of compressed fluid2l) is opened.

ilowing off at the subsequent starting stroke from the working spacesthrough these pressure valves into the discharge pipes yet free frompressure on starting, a so-called pressure maintaining NOW thehand'operated Starting Valve 21 is 25 valve 53 "or 54 respectively isarranged behind the opened for a short time and thereby the ustartingspace I2 is lled with uid under pressure. lAs soon as the pressure inthespace I2 has reached atmospheres superatmospheric pressure, the overflowvalve 45 opens, so that now fluid under pressure may .enter the workingspace 42 of the releasing device 4I. When the pressure in the space -42has reached 2 atmospheres superatmos` pheric pressure, the piston 4Iovercomes the action of the spring 43 and draws the pawl 33 away 35mains closed on starting but in the normal Op from the catch 3l. Thepressure now existing in the 'starting space I2 is able to'displace theflying mass 4, 5, 6. The starting operation is vthereby initiated. Thepressure in the starting space I2 cannot surpass in this case thepressure of 20 atn mospheres superatmospheric pressure, to 'whichg theoverflow valve 45 is adjusted, becausethis valve vopens as soon as thispressure is reached,

and the excess of fluid will ow off to the releas-v ing device or Shouldthis valve d5 fail to open, the pressure in space I2 would increase atmost to the pressure of atmospheres superatmospheric pressure,established by the reduction Valve 25. This in- Volves a double safetydevice against the forma- 5 tion of an excessive pressure in thestarting space I2. A safety guard preventing the pressure in the spacei2 from becoming too low is warranted by the fact that the releasingdevice 'di acts only when it is charged with a pressure of 2 atmos- 55pheres superatmospherie pressure, required for overcoming the pressureof the spring 43. This pressure, however, can only take place when theoverow valve 45 opens, that is when the starting through the safetyvalve 46.45

- pressure valves of each compression stage. Each 80 the valve side withthe pressure of the discharge pipe and on the other side by a spring 59.The action of the spring is greater than the pressure v of the startinggas acting 'on the valve disk. Consequently the pressure-maintainingvalve reeration during which the full iinal pressure of thecorresponding compression stage permanently prevails this valve iscontinuously kept open by this pressure.

The means for supplying fluid under pressurev to the space I2 aresimilar to those shown in Fig. 1. The space I2 is again connected to the`duct leading to the overflow valve 45. From the latter a pipe 60 leadsto the workingspace 8. This space is connected by a duct G2 to an overowvalve di, from which a pipe 36 leads to the releasing space 42.Furthermore a pipe 3l is branched oli from pipe 36 leading to the safetyo valve which opens into the open air.

1 For the pressures the following numerical values may be assumed:

Atmospheres space 'I2 is lled with iiuid under pressure up to 60 Highest'admissible pressure in the starting the lower limit of pressure (20atmospheres superatmospheric pressure). Should the device di fail torelease (for instance, by getting jammed or for pressure. This means'that also in this vcase an ,m

effective safeguard against the formation of an excessive pressure inthe releasing space d2 is established.

Fig. 2 shows a modification in which the comsuperatmospheric pressureHighest admissible pressure in the starting v space I2 25 Lowestadmissible pressure inthe starting space i2 20 space l6Lowest'admissible pressure in the starting space 2 4 {lorrespondinglyuThe reduction valve 25 is adjusted to 25 The overilow valve d5 isadjusted to 20 The overow valve al is adjusted'to 4 Furthermore i Thesafety valve d5 may be adjusted to-- 2 The releasing 'member 4I may beadjustedto 1 When the pressure in the high-pressure starting space i2 onsupplying the uid under prespresser part of the engine is formed as amulties sure has attained 20 atmospheres superatmospheric pressure, theoverilow valve EB opens and pressure in pipe 38 has attained 1atmosphere superatmospneric pressure. At this moment the high-pressurestarting spaceI I 2 is lied with compressed rluid under a pressure o! 20atmospheres superatmospheric pressure, the low-pressure starting space swith compressed fluid under a pressure of 4 atmospheres superatmosphericpressure. This lling of the two starting spaces with compressed iluidunder the pressure intended for them, respectively, automatically takesplace on opening the hand-operated starting valve 2'I. Depending uponthe pressure-reducing valve 25, the maximum pressure inthe startingspace l2 cannot exceed the value of 26 atmospheres superatmosphericpressure, in case the overilow valve its should fail to open. Likewisethe pressure in the low-pressure starting space e cannot assume anexcessive value should the releasing device 4I fail to operate, becauseit'is allowed to drop owing to the overilow valve 4l and the safetyvalve 46; 'moreover the upper limit ofthe pressure in the releasingspace t2 is also determined by the safety valve 45.

If it is desired to doubly safeguard the lowpressure starting spaceagainst excessive pressure, the arrangement shown inFig. 3 may beadopted. Again the overflow valve 45 is connected to the outlet 34 ofthe high-pressure starting space I2. Into the pipe 50 coming therefrom apressurecontrolling device 65 is inserted, which is ad- 'justed in sucha' manner that in its outlet 5I connected with the low-pressure startingspace 8 only the highest pressure admissible in this space can occur.Further, a safety valve 65 communicating with the open air is connectedto a pipe 68 branched oi from pipe 60. At the point where the pipe elcommunicates with the space 8, advantageously a check-valve 64 may beprovided in order to keep away the variations in pressure occurring inspace 8 during the normal operation from the pressure-controlling device65. The numerical example `given in connectionwith Fig. 2 is thereforeto be completed as follows:

Atmospheres superatmospheric pressure The pressure-controlling device 65between the two starting spaces is adjusted to 6 The safety valve 6.6before the device B may be adjusted fn 18 diilerent working spaces thatare lled with fluid under diileren'tpressures are used for starting,

a simplification is possible in some cases, for example, if the lowerlimit of pressure in the starting space having the lowest pressure isequal to zero, i. e., if the engine scarcely starts at a presfsure ot 0atmospheres superatmospheric pressure,

existing Yin this starting space, but-it is desired that this workingspace also participate inthe starting operation. p

In this case the arrangement shown in Fig. 4 may be adopted whichdiffers from that shown in Fig. 2 by the space Il working with the lowerlstarting pressure being immediately connected with the releasing space42 over the pipe $5, without the intermediary of an overflow valve. 'Icthis pipe 36 merely the safety valve 6I leading to the open air isconnected over the branchpipe S1.

For this example the following numerical values The overow valve 45 isadjusted to-- 20 The safety valve 46' behind the low-pressure startingspace is adjusted tos---" 6 Further the releasing member 4I may be ad-Justed to In this case the operation of the device is as follows:

In the normal casethe pawl 33 is released when the pressure inuencingthe releasing member II has attained the value of 4 atmospheressuperatmospheric pressure. The same pressure then acts in thelow-pressure starting space 8, whereas in the high-pressurestartingspace I2 a pressure of 20 atmospheres superatmospheric pressure, isacting. Should it now occur that due to a defect of the releasing memberas, for instance, relaxation in force of the spring the releasing of thecatch 33 takes place at a pressure essentially lower than the pressureof 4 atmospheres superatmospheric pressure, provided for this releasingoperation, for instance, at V2 atmosphere superatmospheric pressure, itis true that likewise only a pressure of Vgfatmosphere superatmosphericpressure, assists in starting, but the engine is nevertheless set inmotion,'because the starting pressure of 20 atmospheres superatmosphericpressure, existing in the high-pressure starting space 12 just sumcesfor starting.

We claim:

1. In a device for starting a free piston motor compressor by means ofuid under pressure, said compressor having a flying mass formed bypistons displaceable in stationary cylinders and forming with saidcylinders a plurality of working spaces, the combination oi.' a lockingdevice for holding said flying mass in its dead center position; acontainer illled with said fluid under pressure; a pipe lineconnectingsaid container with a, selected one of said working spaces: a

` releasing device `adapted to be infiuencedby said fluid under pressureand to release said locking device; a second pipe line connecting -saidsereleasing device when the pressure in said space exceeds apredetermined limit.

2. In a device for starting a iree'piston' motor .sure of said fluid incompressor by means of fluid under pressure; said compressor having aiiying mass formed by pistons displaceable in stationaryv cylinders andforming with said cylinders a plurality of worklng spaces, thecombination of a, locking device for holding said flying mass in itsdead center position; a container filled with said fluid under pressure;a pipe line connecting said container with a selected one of saidworking spaces; a releasing device adapted to be iniiuenced by said uidunder pressure and to release said locking device; a second pipe lineconnecting said selected working space with' said releasing device;means in said second pipe line for releasing fluid pressure from saidselected space to said releasing device when the pressure in said spaceexceeds a determined upper limit; and means for maintaining saidreleased pressure below a second determined pressure limit lower thansaid rst limit.

with a selected one of said working spaces; a pressure-controlling valvein said pipe line, adjusted to maintain the pressure of said fluid insaid selected working space below a determined upper limit; a releasingdevice; a vsecond pipe line connecting saidselected working space withsaid releasing device, and pressure controlling means in said secondpipe for releasing pressure from said selected space into said releasing-device at a pressure below said upper limit.

4. In a device for starting a free piston motor compressor by means ofuld under pressure, said compressor having a flying mass formed bypistons displaceable in forming with said cylinders a plurality ofworking spaces, the combination of a. locking device for holding saidiiying mass in its dead center position; a, container filled with saidfluid under pressure; a pipe line connecting said container with aselected one of said working spaces; a releasing device adapted to beinuenced by said fluid under pressure and to release said lockingdevice; a second pipeline connecting said selected working space withsaid releasing device;

and an over-flow valve in said second pipe line, i

adjusted to maintain the pressure of said uid in said selected workingspace below a predetermined limit.

5.- In a device for starting-a. free piston motor compressor by means ofuid under pressure, said compressor having a flying mass formed bypistons displaceable in stationary cylinders and forming with saidcylinders a plurality of working spaces, the combination of a lockingdevice for holding said flying mass in its dead center position; acontainer filled with said fluid under pressure; a pipe line connectingsaid container with a selected one of said working spaces; an adjustablereleasing device adapted to be influenced by said uid under pressure andto release said locking device; a second pipe line connecting saidselected working space with said releasing device; and an over-flowvalve in said second pipe line, adjusted to maintain the pressaidselected working space below a predetermined limit, said releasing deapipe line connecting said container -stationary cylinders and w 10 vicebeing adjusted to release said vice when inuenced by the fluid under apressure above said predetermined limit. v

6. In a devicer for starting a free piston motor compressor by means offluid under pressure, said compressor having` a flying mass formed bypistons displaceable in stationary cylinders and, forming with saidcylinders a plurality of working spaces, Athe combination of for holdingsaid flying mass in its dead center position; a container filled withsaid fluid under pressure; a pipe line connecting said container with aselected one of said working spaces; an adjustable releasing deviceadapted to be inuenced by said iiuid under pressure and to release saidlocking device; a second pipe line connecting said selected workingspace with said releasing device; an over-now valve in said second pipeline, adjusted to maintain the pressure of said fluid in said selectedworking space below a predetermined limit, said releasing device beingadjusted to release said locking device'when inuenced by the fluid undera pressure above said predetermined limit; and a -safety valve in saidsecond pipe line, between and said releasing device, and adapted topermit escape of said fluid from said second pipe line when the pressureof said fluid in said line is above the pressure actuating saidreleasing device and above the said predetermined limit of pressure inthe selected working space.

'7. In a device for starting a free piston' motor compressor by means offluid under pressure, said compressor having a flying mass formed bypistons displaceable in stationary cylinders and forming with saidcylinders a plurality of Working spaces, the combination of a lockingdevice for holding said flying mass in its dead center position; acontainer pressure; a pipe line connecting said container with aselectedone of said Working spaces; a second pipe line connecting saidselected one of said working spaces with a second selected one of saidworking spaces; a releasing device adapted to be influenced by saidfluid under pressure and to release said locking device; and a thirdpipe line connecting said second selected Working space with saidreleasing device.

8. In a device for starting a free piston motor compressor by means ofiiuid under pressure, said compressor having a flying mass formed by.pistons displaceable in' stationary cylinders and forming with saidcylinders a plurality of working spaces, the combination of a lockingdevice for holding said flying mass in its dead center position; acontainer filled with said fluid under pressure; a pipe line connectingsaid container with a selected one of said working spaces; a secondpipeline connecting said selected one of said working spaces with a secondselected onev of said Working spaces; areleasing device adapted to beinfluenced by said fluid under pressure and to release said lockingdevice; a third pipe line connecting said second selected working spacewith said releasing device; and means for maintaining the pressure ofsaid uid in each of said two selected Working spaces within determinedlimits. i

9. In a device for starting a free piston motor compressor by means offluid under pressure, said compressor having a flying mass formed bypistons displaceable in stationary cylinders and forming with saidcylinders a. plurality of working spaces,V the combination of a lockingdevice for holding said fiying mass in its dead center locking dealocking device said over-now valve filled with said fluid under assensoupper limit; a second pipe line connecting said selected one of saidworking` spaces with a second selected one of said working spaces anover-flow valve in said second pipe line, adjusted to maintain thepressure of said :duid in said first 'selected working space above adeterminedlower lmit: a releasing device adapted to be influenced bysaid iiuid under pressure and to release said locking device; a thirdpipe line connecting said second selected working space with saidreleasing device; and an over-now valveA in said third pipe line,adjusted to'maintain the pressure of said iiuid in said second selectedworking space above a determined lower limit.

10. In a device for starting a free piston motor compressor by means ofuid under pressure,

said compressor having a dying mass formed by pistons displaceable instationary cylinders and forming with said cylinders a plurality ofworking spaces, the combination oi' a locking device for holding saidiiying mass inits dead center position; a container filled with saidfluid under pressure: 'a pipe line connecting said container with aselected one of said working spaces; a pressure-controlling valve insaid pipe line, adusted to -maintain the pressure of said :fluid in saidselected working space below a determined upper limit: a second pipeline connecting said selected one of said working spaces with a secondselected one of said working spaces; an over-flow valve in said secondpipe line, adjusted to 1nainl tain the pressure of said iluid in saidiirst selected working space above a determined lower' limit; apressure-controlling valve in' said second pipe line,

between said over-flow valve and said second selected working space,adjusted to maintain the pressure of said fluid in said second selectedworking space below a determined upper` limit:

a releasing device adapted to bev influenced by v said fluid underpressure and to release said locking device; s. third pipe lineconnecting said second selected working space with said releasingdevice; and an over-flow valve in said third pipe line, adjusted tomaintain the pressure of said uid'in said second selected working spaceabove a determined lower limit.

PAUL MILEJANS. FRANZ NEUGEBAUER.

anrEnENcEs CITED The following references are of record in the i'ile oithis patent:

,UNITED STATES PATENTS Number Name Date 2,112,368 Janicke Mar. 29, 19382,222,260 Janicke Nov. 19, 1940 2,086,228 Janicke July 6, 1937 2,038,442Pescara Apr. 21, 1936 2,064,976 Janicke Dec. 22, 1936 2,086,162 JanickeJuly 6, 1937 1,757,215 Pescara May 6, 1930 2,168,828 Pescara Aug. 8,1939 2,215,326 Janicke Sept. 17, 1940 2,282,297 Keller May 5, 1942FOREIGN PATENTS Number Country Date 623,039 Germany 1935 623,038 Germany1935 496,022 Great Britain Nov. 23, 1938 497,999 Great Britain Jan. 2,1939

